Split in Three

input/code.cpp: In function 'void solve()':
input/code.cpp:51:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 100;

int t;
int n;

bool Used[3][MAX_N];
int Sum[3] = {0};
int NeededSum[3];
bool recursionDone;

void recur(int group, int pos)
{
    if(Sum[group] > NeededSum[group])
    {
        return;
    }

    if(Sum[group] == NeededSum[group])
    {
        recursionDone = true;
        return;
    }

    if(pos == n)
    {
        return;
    }

    if(!Used[(group + 1) % 3][pos] && !Used[(group + 2) % 3][pos])
    {
        Used[group][pos] = true;
        Sum[group] += pos + 1;
        recur(group, pos + 1);
        if(recursionDone)
        {
            return;
        }
        Sum[group] -= pos + 1;
        Used[group][pos] = false;
    }

    recur(group, pos + 1);
}

void solve()
{
    scanf("%d", &n);
    if((n + 2) % 3 == 0)
    {
        puts("IMPOSSIBLE");
    }
    else
    {
        NeededSum[0] = (n*n + n - 6) / 6;
        NeededSum[1] = NeededSum[0] + 1;
        NeededSum[2] = NeededSum[0] + 2;
        recursionDone = false;
        recur(0, 0);
        recursionDone = false;
        recur(1, 0);
        for(int i = 0; i < n; i++)
        {
            if(Used[0][i])
            {
                printf("%d ", 1);
            }
            else if(Used[1][i])
            {
                printf("%d ", 2);
            }
            else
            {
                printf("%d ", 3);
            }
        }
    }
}

int main()
{
    t = 1;
    //scanf("%d", &t);
    while(t--)
    {
        solve();
    }
    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: WRONG ANSWER

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 1, 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 2

Verdict: ACCEPTED